Answer : The correct option is, (d) to agitate a solution
Explanation :
Stir bars is a type tool which is used in the chemical laboratory for mixing the solute in the solvent.
Stir bars is a magnet which is covered with such type of material that does not react with any liquid it is immersed in. Its cover is not react for any type of liquids.
The stir bar magnet is placed in a container or flask. The stir bar magnet made to spin with an external magnetic field.
The stir bar magnet is used in the laboratory to agitate a solution.
Hence, the correct option is, (d) to agitate a solution